Thats totally subjective............. ive heard of people going as big as 100x turnover rates..obviously its got to be BB to do that or it would be a sandstorm.
Im setting up a sps tank right now with about 40-45x turnover. Its 90 gallon and im running a mag 12 in the sump, and a pcx 40(1050) AND a sequence dart (3600)on the cls.
I dont think you want any less than 20x if its just sps.
Im not familiar with that pump youre talking about, but its defintely not too big as far as flow is concerned.
revised answer....i didnt catch the 50 gallon part..............I thought it said 80 at first glance.............im going to change my last sentence from "definitely" to...i dont think it is too big. I think it would work great for a sps tank as far as flow.
I had 2200gph in a 55 and wanted more. The tunze also puts the output over a wide area instead of a narrow stream which is good. I think you are fine. In a SPS dominated system the more the better! SPS are from the front of the reef and that environment has a LOT of flow. Waves, current etc. SPS like flow, dont sweat it! As long as they arent blown off of the rrock they will be fine!